U.S. patent application Ser. No. 09/605,520 (“the '520 application”) describes in detail the use of elastomeric materials to fabricate microfluidic structures. The '520 application is hereby incorporated by reference in its entirety for all purposes.
The microfabricated elastomeric structures disclosed in the '520 application may be employed for a wide variety of purposes. One application for which these structures are particularly suited is sorting. In a sorting structure, a sample containing a sortable entity is flowed down a flow channel to a detection region, such that only one sortable entity may be located within the detection region at a time. The detection region is then interrogated to identify the sortable entity. The sortable entity is then flowed to a junction, and then down one or another branch at the junction based upon the identification process.
As described in the '520 application, the width of the flow channels may be defined utilizing photolithographic techniques conventionally employed in semiconductor fabrication processes. Accordingly, the dimensions of the flow channels may extremely small (<1 μm), allowing for sorting of entities on the cellular or molecular scale.
One of the most important steps of a sorting process is the accurate detection and identification of an entity prior to its sorting. This detection/identification task is made more difficult when the entity is extremely small.
Accordingly, there is a need in the art for methods and structures for detecting and identifying the contents of the extremely narrow flow channels of microfluidic devices.